Hotel indoor pool CC not coming down

[JordanB]

I started a few months ago as the maintenance manager at a hotel and am in charge of maintaining the indoor pool. It’s 21000 gallons and for the first few months I had no trouble with the chemistry. For the last 3 weeks the CC has been steadily climbing from an average of .2ppm up to a peak of 2.45ppm. Nothing has changed with our setup so I’m puzzled. FC: 2.65 TC: 5.10ppm CC: 2.45ppm. pH: 7.5. Alk: 110ppm. We use sodium hypochlorite (liquid) to sanitize and it’s on an auto feed system. We purchase the chlorine approximately every 3 weeks so it doesn’t sit on the shelf too long.
I attempted to reach breakpoint chlorine in an effort to bring CC levels down and found a calculator online. Based on calculations, I added 4.27 gallons of 12% sodium hypochlorite all at once. I should also say I lowered the pH to 7.2 prior to adding this……Anyways, I don’t exactly know how high the chlorine went as our BECSys3 maxes out at 16 and our Palintest Pooltest 6 maxes out at >10ppm……Pool was shut down for 30 hours with circulation pump running, fans set up on the pool deck and all 4 roof air exchangers turned on high. 30 hours later chlorine levels were still extremely high and my manager wanted the pool opened asap. I added X-It, a chlorine removal chemical to bring levels down however once they were low enough, CC was still present and high. Current readings are: FC: 4.98ppm TC: 6.75ppm and CC: 1.77ppm. PH is back to 7.5
Should I have waited longer than 30 hours? Will the CC levels drop if I add more X-IT and bring the chlorine down further? Ideally we keep the FC around 2.5ppm so it needs to be lowered a little more anyway. Please let me know.

 

[JordanB]

I should also say CYA is at 2ppm, would that have any affect on this?

 

[Bperry]

I started a few months ago as the maintenance manager at a hotel and am in charge of maintaining the indoor pool. It’s 21000 gallons and for the first few months I had no trouble with the chemistry. For the last 3 weeks the CC has been steadily climbing from an average of .2ppm up to a peak of 2.45ppm. Nothing has changed with our setup so I’m puzzled. FC: 2.65 TC: 5.10ppm CC: 2.45ppm. pH: 7.5. Alk: 110ppm. We use sodium hypochlorite (liquid) to sanitize and it’s on an auto feed system. We purchase the chlorine approximately every 3 weeks so it doesn’t sit on the shelf too long.
I attempted to reach breakpoint chlorine in an effort to bring CC levels down and found a calculator online. Based on calculations, I added 4.27 gallons of 12% sodium hypochlorite all at once. I should also say I lowered the pH to 7.2 prior to adding this……Anyways, I don’t exactly know how high the chlorine went as our BECSys3 maxes out at 16 and our Palintest Pooltest 6 maxes out at >10ppm……Pool was shut down for 30 hours with circulation pump running, fans set up on the pool deck and all 4 roof air exchangers turned on high. 30 hours later chlorine levels were still extremely high and my manager wanted the pool opened asap. I added X-It, a chlorine removal chemical to bring levels down however once they were low enough, CC was still present and high. Current readings are: FC: 4.98ppm TC: 6.75ppm and CC: 1.77ppm. PH is back to 7.5
Should I have waited longer than 30 hours? Will the CC levels drop if I add more X-IT and bring the chlorine down further? Ideally we keep the FC around 2.5ppm so it needs to be lowered a little more anyway. Please let me know.

Assuming the CC test is accurate, the water is unsanitary at over 2ppm CC and may cause skin irritation. What’s the active ingredient in the x-it product? Have you used any non-chlorine shock(MPS)?

What do your local regulations say you have to do with water chemistry? (May not be able to follow residential guidelines that TFP is geared for)

 

[Bperry]

I should also say CYA is at 2ppm, would that have any affect on this?

Has any chlorine stabilizer (CYA) been added to the water? I’ll admit the test methods you are using are known to not be very reliable, but you may be stuck with them depending on commercial regulations.

 

[JordanB]

Assuming the CC test is accurate, the water is unsanitary at over 2ppm CC and may cause skin irritation. What’s the active ingredient in the x-it product? Have you used any non-chlorine shock(MPS)?

What do your local regulations say you have to do with water chemistry? (May not be able to follow residential guidelines that TFP is geared for)

Local regulations say CC must be below 1.5ppm which is why I was attempting to reach breakpoint to lower. Active ingredient in X-it is sodium sulfite. It works really well to lower chlorine levels quickly. TC maximum allowed is 5ppm.

 

[JordanB]

Has any chlorine stabilizer (CYA) been added to the water? I’ll admit the test methods you are using are known to not be very reliable, but you may be stuck with them depending on commercial regulations.

No stabilizer has been added as this is an indoor pool with zero windows so no sunlight exposure.

 

[mknauss]

Does the pool have a UV system to eliminate CC?

 

[ajw22]

Best thing to do is drain the pool and refill it with fresh water and start over.

 

[JordanB]

Does the pool have a UV system to eliminate CC?

No, it does not.

 

[JamesW]

In my opinion, an indoor commercial pool has to use a properly sized commercial UV or Ozone System as a supplemental oxidizer or you will never get rid of persistent CCs.

What is the usage on a daily basis?

Note: Ozone needs to be done properly and not just pumped into the return lines.

It requires a legit commercial installation including a mixing tank and a degas process.

 

[JordanB]

Best thing to do is drain the pool and refill it with fresh water and start over.

Pool was drained and refilled less than 2 months ago. Everything was fine for about a month after and then CC started creeping up regardless of where the FC was set.

 

[JordanB]

In my opinion, an indoor commercial pool has to use a properly sized commercial UV or Ozone System as a supplemental oxidizer or you will never get rid of persistent CCs.

What is the usage on a daily basis?

Note: Ozone needs to be done properly and not just pumped into the return lines.

It requires a legit commercial installation including a mixing tank and a degas process.

Pool is 30 years old and has never had issues. I started in august and had no issues until about 3 weeks ago.

 

[ajw22]

Pool was drained and refilled less than 2 months ago. Everything was fine for about a month after and then CC started creeping up regardless of where the FC was set.

Pool is 30 years old and has never had issues. I started in august and had no issues until about 3 weeks ago.

You sure some system has not broken? Like a UV or Ozone system you are not aware of?

 

[JamesW]

Humans excrete a bunch of different carbon and nitrogen based molecules and these can combine with chlorine to create DBPs.

Disinfection by-products (DBPs) are formed when disinfectants like chlorine interact with natural organic materials in water, such as in chlorinated drinking water and chlorine-treated swimming pools.

DBPs can be found in the air during activities such as showering, bathing, dishwashing, and swimming.

The most common type of DBPs are trihalomethanes (THMs).

 

[Bperry]

Local regulations say CC must be below 1.5ppm which is why I was attempting to reach breakpoint to lower. Active ingredient in X-it is sodium sulfite. It works really well to lower chlorine levels quickly. TC maximum allowed is 5ppm.

Even though it’s a commercial pool, you’de benefit from a more reliable testing kit like a Taylor K2006C, as it’ll let you test FC and CC much higher and more reliably. Maybe hard to get in Canada? TFP is oriented towards only trusting one specific testing method because most/all of the others have been proven unreliable.

 

[JamesW]

Pool is 30 years old and has never had issues.

Unless you were there, how do you know that there were no issues?

In any case, my opinion is that a high use indoor pool needs UV or you will have persistent chlorinated products that are persistent over long periods of time.

What is the usage on a daily basis?

 

[JamesW]

You should get an FAS-DPD test kit.

Do you use MPS?

Can you smell the chloramines?

 

[JamesW]

I should also say CYA is at 2ppm, would that have any affect on this?

How are you getting a reading of 2 for CYA?

What are you keeping the ORP level at?

Does the BECSys3 system chlorine reading match your drop test kit results?



The controller has an optional free chlorine sensor, which can be selected for sanitizer feed control rather than ORP.

If using ORP, a derived chlorine ppm display is also available, which provides an approximation of the residual chlorine level on a 0.2 to 16 ppm scale.

The BECSys3 can also be configured without a PPM scale, displaying only the pH and the ORP readings only.

Do you have the optional free chlorine sensor?

Every controller comes complete with either pH and ORP sensors or pH, free chlorine and temperature sensors, flow switch, machined flow cell, and factory-trained start-up and support provided by local distribution in most regions.

 

[Divin Dave]

If accurate, those are some pretty high CCs.
Question: How does the water smell? When you go into the pool room, does your nose instantly say YUK? If there is an unpleasant scent, then the CC are definitely very high. It is the CC's that a lot of non-savvy people call "chlorine" smell that they object to. A sanitary and clean pool will smell fresh and pleasant with perhaps a very slight scent of fresh chlorine.

It's up to you to go this route or not, but I would highly recommend getting this FAS DPD test kit. It will provide accurate measurements up to 50ppm. You can really get a good grip on your chlorine levels using this kit.

FAS/DPD Chlorine Test Kit

tftestkits.net

I suggest also doing an Overnight Chlorine Loss Test. Since the pool is indoor, maybe you can do this during the day, but the pool must be closed, no swimmers. If there are large windows that the sun shines directly through, then cover them. Do not do anything, at all, to the pool during this test. If there is a Skylight in the pool room ceiling, then you'll have to do this test at night.
Take a FC test (we do this at night to eliminate UV from the sun burning off chlorine).
10-12 hours later (or for us early the next morning before sunrise), test the FC again.
There should be No More Than 0.5ppm loss of FC.
If the FC loss exceeds 0.5, then there are organics in the water that is consuming the FC, and causing the high CC test results.

Maybe this calculator may be of some help to you also. At the bottom of the calculator is a category named "Effects Of Adding Chemicals". At the top of the calculator, you will need to enter the volume of your pool for the calculator to be accurate. You can play around with this so as to have an accurate expectation of results of a test before you add any chemicals.

PoolMath

Discover the calculator behind the perfect pool, PoolMath. Dealing with pools has allowed TFP to become the original authors of the best calculator on the net.

www.troublefreepool.com

 

[JamesW]

Pool is 30 years old and has never had issues.

Maybe that is what they told you, but it is highly unlikely.